They are for old "Dunlop" or "Woods" valves, that were halfway in size between a presta & schrader valve. Just inside the cap (that you could screw off) was the rubber tube that acted as the valve. If it split or broke (usually when the rubber perished) you could replace it and be on your way again.
We have Dunlop valves described in the Terminology Index, and you can find more out at Wikipedia.